WORK AND SIMPLE MACHINES

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WORK AND SIMPLE MACHINES

• Life Made Easier

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WHAT IS WORK?

• Work occurs when a force causes an object to move
  in the same direction the force is applied

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SO WHAT DO MACHINES HAVE TO DO WITH WORK?

• A machine is
• a device that helps make work easier by changing
  the size or direction of the force

• When you use a machine, you do work on the
  machine and the machine does work on something
  else

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• Basically, machines make it easier to do things
  like
• Lifting a piano by yourself
• Splitting a piece of wood
• Moving a boat using only human power

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INPUT AND OUTPUT FORCE

• Input force the force you apply to the machine
• Output force the force the machine applies to
  something else
• In diagrams showing how machines work, the
  thickness of the arrows shows the strength of the
  force and the length of the arrows shows the
  distance over which the force is applied

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FOR EXAMPLE
A long weak input force results in a shorter
stronger output force
A short strong input force results in a longer
weaker output force
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TYPES OF MACHINES

• All machines are constructed from 6 simple
  machines
• A compound machine a machine made of 2 or more
  simple machines

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LEVERS

• General Description
• Consists of a bar that pivots (turns/moves) at a
  fixed point called a fulcrum
• Come in 3 types
• How they help us
• Lift or move heavy loads using less force

Fulcrum
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1st CLASS LEVERS

• Description
• Fulcrum is between the input force and the load
  (what youre trying to move)
• Input and output force are always in opposite
  directions
• Examples
• Oars in a boat
• Kids on a seesaw
• Using a hammer to remove a nail
• Scissors

Fulcrum
Input force
Output force
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1st CLASS LEVERS
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2ndCLASS LEVERS

• Description
• The load is between the fulcrum and the input
  force
• Examples
• Lifting a load with a wheelbarrow
• Removing a bottlecap
• Light switch

Fulcrum
Input force
Output force
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2nd CLASS LEVERS
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3rdCLASS LEVERS

• Description
• The input force is between the fulcrum and the
  load
• Examples
• Hitting a nail with a hammer
• Using arm to curl a barbell (elbow)

Fulcrum
Input force
Output force
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3rd CLASS LEVERS
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LEVERS a simple comparison
2nd
1st
3rd
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INCLINED PLANES

• Description
• A straight slanted surface
• How it helps us
• Make it easier to go up or down
• Examples
• Ramp
• Slide

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WEDGES

• Description
• A double inclined plane that moves
• How it helps us
• Cut or push two objects apart
• Examples
• Knife
• Doorstop
• Axe heads
• Chisel
• Plow

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SCREWS

• Description
• Inclined plane wrapped in a spiral
• When rotated, the screw applies a large force
  through the short distance it is pushed
• How it helps us
• Holds things together
• Lifts things using less force
• Examples
• Screws
• Bolts
• Jar lid
• Corkscrew

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WHEEL AND AXLE

• Description
• Consists of a large wheel securely attached to a
  smaller wheel or shaft (the axle)
• When the wheel or axle turns, it causes the other
  part to turn as well
• How it helps us
• Lift or move loads using less force
• Examples
• Doorknobs
• Ferris wheels
• Steering wheels
• Wheels on cars, buses, planes

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PULLEYS

• Description
• Consists of a grooved wheel that holds a rope or
  a cable
• How it helps us
• Moves things up, down, or across
• Examples
• Elevators
• Flag poles
• Mini-blinds
• Tow trucks

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COMPOUND MACHINES

• These are made of two or more simple machines
• Examples
• Can opener (wheel and axle, wedge, second class
  lever)
• Scissors (wedge first class lever)

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RUBE GOLDBERG
As Tailor (A) fits customer (B) and calls out
measurements, college boy (C) mistakes them for
football signals and makes a flying tackle at
clothing dummy (D).   Dummy bumps head against
paddle (E) causing it to pull hook (F) and throw
bottle (G) on end of folding hat rack (H) which
spreads and pushes head of cabbage (I) into net
(J).   Weight of cabbage pulls cord (K) causing
shears (L) to cut string (M).  Bag of sand (N)
drops on scale (O) and pushes broom (P) against
pail of whitewash (Q) which upsets all over you
causing you to look like a marble statue and
making it impossible for you to be recognized by
bill collectors.    Don't worry about posing as
any particular historical statue because bill
collectors don't know much about art.
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THE GREAT RUBE GOLBERG MACHINE PROJECT

• Helpful hints
• Use your class time wisely
• Be creative and have fun!
• Use simple junk lying around at home
• Keep all drafts of your ideas, drawings, etc.
  the inventing process is what I want to see
• A Rube Goldberg device in action
• Another series of Rube Goldberg devices

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Works Cited

• Slide 4 (http//www.braymore.ca/Delivery/gallery-m
  oving.htm)
• Slide 10, 12, 14 (http//en.wikipedia.org/wiki/L
  ever)
• Slide 16 (http//www.amusements.com/ferriswheel.ht
  ml)
• Slide 17 (http//fla.fg-a.com/flags1a.htm)
• Slide 19 (http//www.rube-goldberg.com/html/dodgin
  gthebillcollector.htm)